AN3157

3-phase systems

Doc ID 17105 Rev 1

21/26

A.2.2

Three-wattmeter method

This method is used in a 3-phase four-wire balanced or unbalanced load. The connections

are made with one meter in each line as shown in Figure 15. In this configuration, the total

active power supplied to the load is equal to the sum of the three wattmeter readings.

A.2.3

One wattmeter method

This method is suitable only in 3-phase four-wire balanced loads. The connection of the

wattmeter is similar to the drawing in Figure 15. The total power is equal to three times the

reading of only one wattmeter which is connected between one phase and neutral.

3

2

1

Total

P

P

P

P

+

+

=

Figure 15.

The wattmeter connections in 3-phase four-wire loads